Going from a 1G to 3G Alternator

So after reading all I could about swapping the old Ford 1G alternator for the newer and more powerful 130A 3G alternator, I’d figured this would be way easy… and it should have been.

Several years ago I replaced all my wire harnesses with brand new ’66 reproductions.I also purchased the PA Performance upgrade kit which includes the 3G wire harness pigtail as well as the replacement external voltage regulator that is supposed to capture the current and reroute it to the new 3G.

Installing the 3G alternator was a snap as I was able to purchase one that fit into the billet brackets on my engine.Fairly sure this would also work with the stock brackets.I did have to remove the serpentine pulley and install the v-belt pulley.I opted for a single pulley in spite of reading how these tend to ‘squeal’ but I have had no issues to date with the single v-belt setup.

Following the instructions on how to wire Pas 3G harness to the 3G alternator was a snap… I also purchased the PA mega fuse and cable to charge the battery.Very important to do this as the new alternator is sending a shipload more power to the battery and the original wire would simply burn up.

Replacing the original external voltage regulator with PA’s replacement was self-explanatory. Simply remove and replace.

When we fired up the engine (for the first time since 2004) and checked the gauges, I found that I was not getting proper reading on my voltmeter.So for two weeks I went over everything and scoured the message boards for info and help… and nobody could tell me anymore than how to follow the directions... which I did… and then finally the cause of the frustration jumped out at me like a kangaroo in heat…. It turns out that the wire harness I used to replace the old 50 year old harness was wired incorrectly at the external voltage regulator plug…

They had the yellow and the white wires reversed.I guess that happens… and luckily the replacement dummy regulator uses diodes so current can only go in one direction so there was no damage in sending 12 volts from the battery into the field output tab…

All this time I couldn’t figure out why the hell my charging system wasn’t working when I knew damned well I had hooked everything up proper… my mistake was assuming the harness I purchased from (major mustang parts supplier) was correct… which it turns out was the source of my frustrating ordeal.

So take note… check everything twice…even the stuff you buy.

Included are two schematics… one showing the original ’66 Mustang wiring and the other showing how to eliminate the voltage regulator all together… if you simply wish to jump to a 3G alternator and don’t care about retaining stock wiring… then what follows is for you.If you wish to upgrade to 3G and don’t want to cut any wires and/or will be using stock gauges then simply follow along with the provided instructions from PA.

Retaining Original Wiring and/or Gauges

In a nutshell, assuming you purchased the PA kit, disconnect battery and remove old alternator.Disconnect the alternator wire harness at the three wire connector (white, black/yellow and black/red).

Remove the external regular (two bolts) and unplug the harness.Plug the harness into the PA replacement regulator and reattach to radiator support.

Install new 3G alternator after you connect the new PA 3G harness and heavy gauge mega-fuse charging cable to the new alternator following PA’s instructions.The only splice needed is the one where you connect the PA green/red wire to the White wire on the three wire connection where the old alternator harness plugged into.

NOT Retaining Original Wiring and/or Gauges HOWEVER, if you wish to remove all the unnecessary wires, then you would order just the PA 3G harness and that will come with the proper resistor installed on their green/red wire (this is done in the dummy regulator for those of us who bought the kit).

The schematics show which wires can be removed and/or repurposed, especially if you are going with aftermarket modern gauges.If you bought the kit and later decide to remove the regulator and nonessential wires like I did, then you must employ the use of the proper 440K ½ watt resistor on that Green/red line to the new 3G alternator.